Fifteen years ago, Zao Wou-ki’s paintings could be found in Parisian galleries for $50,000 or less.

Now they fetch more than $1 million at auction, with the strongest works going for as much as $8 million.

“Back in the 1990s, I was so picky. I’d go to Paris and find the big masterpieces,” said Victor Ma, a Taiwanese financier and collector whose 100-plus Zao works adorn the walls of his office and home. “No more. The Taiwanese and Chinese, they’ve bought it all.”

Zao Wou-ki

’10.6.68′ sold for $8.8 million at a Sotheby’s sale in Hong Kong last year. View slideshow

Mr. Zao, 92 years old and cared for in a town outside Geneva by his third wife, is too frail to paint anymore. (His wife, Francoise Marquet, said he was not available to comment because of his poor health.) But he is experiencing greater fame than ever before, the result of nearly 10 years of growing interest among Chinese collectors. Last year, according to Artprice, he was the top-selling, living Chinese artist at auction, generating $90 million for his work and outpacing contemporaries such as Zeng Fanzhi and Zhang Xiaogang.

Two galleries are seizing on his late-career popularity to show watercolors he produced just before his retirement in 2009. Feast Projects in Hong Kong opens its show, “Beyond,” on Friday, followed by “Le temps de collections,” at the Musée des Beaux-Arts in Rouen, France, a group show including his works that begins Oct. 12.

The paintings — which vary from blurs of color to jagged brushstrokes across the canvas — have never been shown before. “This is his last major output,” said Feast Projects owner Philippe Koutouzis, noting that Mr. Zao gave up oil painting in 2004 but continued to use watercolors for several years. “It’s still very much Wou-ki.”

Mr. Zao was born in Beijing in 1920. Encouraged by his father, an amateur artist, he began studying traditional ink painting and calligraphy as a teenager. At 15, he enrolled in an arts school in Hangzhou, where he met his first wife Lan Xiejing, a fellow artist who went by the name Lalan. Mr. Zao finished his training at the school, which moved to Chongqing in 1938 to escape the Japanese invasion, and after graduation, became a teacher at the institution.

But he pined for Europe, and with his family’s blessing, he and Ms. Lan moved to Paris in 1948. After a 34-day voyage from Shanghai, he made it to the French capital, dropped their bags at a hotel, and went straight to the Louvre museum that afternoon, according to a biographical essay by French art historian Jacque Leymarie.

Mr. Zao quickly fell into French arts circles: He rented a studio next to sculptor Alberto Giacometti, and became friends with artists such as Joan Mitchell, Jean-Paul Riopelle and Pierre Soulages.

He befriended writers Henri Michauxand Andre Malrauxand, later in his life, regularly dined with French president Jacques Chiracand Prime Minister Dominique de Villepin. “So many artists are narcissists, but he’s not. He’s a very curious man,” said Ms. Marquet, his current wife.

In 1951, he discovered the color-drenched paintings of Paul Klee, a major influence on Mr. Zao’s work that prompted his turn toward abstract art. New York dealer Samuel Kootz, who at the time represented Jackson Pollockand Mark Rothko, started exhibiting Mr. Zao’s works in 1959.

Mr. Zao split from his first wife in 1957, and married his second wife, sculptor Chan Ma-Kan, the following year. She committed suicide in 1972 and after her death, he returned to China for the first time since his move.

In April 1973, back in France, Mr. Zao met Ms. Marquet, a curator who was 26 years his junior. By the end of the year, they were living together. They married in 1978.

Mr. Zao’s profile continued to rise. He donated 80 prints to the Bibliotheque Nationale de France, and he continued to mount exhibitions at galleries during the 1980s, including a retrospective in Hong Kong and a triptych produced for the newly opened Raffles City building in Singapore, which was designed by longtime friend I.M. Pei.

But by the 1990s, interest among galleries and museums was flagging. Mr. Koutouzis said he recalled one dealer in Geneva cutting prices to clear his Zao inventory. “There was a long plateau period,” said Ms. Marquet. “Museum directors in the U.S. and France would tell him they weren’t interested in abstraction. He was out of fashion.”

But Mr. Zao, a bon vivant nicknamed “Zao Whiskey” by his doctor, kept to a rigorous daily routine, continuing to paint seven days a week. “We’d rarely go on vacation,” Ms. Marquet said.

He often focused on one canvas for weeks at a time, a pace that explains why his output is lower than that of other contemporary painters. Mr. Zao’s lifetime oeuvre consists of some 1,800 oil paintings on canvas, compared with 3,000 works by Gerhardt Richter, the world’s current top-selling living artist, who continues to paint.

“He’s like Dustin Hoffman in ‘Rain Man,’” said Mr. Ma, the Taiwanese collector, who visited Mr. Zao many times and used to call him every other week for informal chats. “All his brainpower is in art, but nowhere else.”

Mr. Zao experienced a resurgence in 2003 with a flurry of exhibitions. Marlborough Gallery in New York showed a collection of his new works, marking his first U.S. show in more than 10 years, followed by private gallery shows in Paris and Hong Kong, and a retrospective at the Jeu de Paume Gallery in Paris.

Collectors followed suit. In 1999, an untitled 1962 abstract sold for just $15,254 at a Christie’s sale in London. By 2003, another untitled work sold at Doyle New York for $388,300. Two years later, a triptych sold at a Christie’s sale in Hong Kong for $2.4 million. In 2008, his work “Hommage à Tu-Fu” sold at a Hong Kong auction for $5.9 million, up from the $46,000 it commanded at a 1992 Paris sale.

Last year, prices for his work reached a new high when Sotheby’s sold his painting, “10.6.68,” for $8.8 million. “Zao is the first 20th-century Chinese artist with an international reputation,” said Sylvie Chen, a modern Chinese art expert at Sotheby’s. “We do predict prices to rise. There’s very limited supply.”

Mr. Ma attributes Mr. Zao’s surge in popularity to his becoming a status symbol among wealthy Chinese. “All the rich Taiwanese want a big, abstract horizontal painting in the hall of their homes,” he said. “People have always known of him, but until recently, the star in the art market was always Zhang Daqian. Now, it’s Mr. Zao.”

Pascal de Sarthe, a Hong Kong gallery owner who has dealt many of Mr. Zao’s works since the 1980s, said the interest among Chinese collectors mirrors how American collectors championed Pollock and Rothko in the post-war era.

“American buyers defended their own artists,” he said. “The Chinese will do the same. It’s not normal for him to be priced below a Rothko or a Pollock. Nationalism will push him up.”